1. Field of Invention
This invention relates to a noise filter. In particular, this invention relates to a noise filter that is securely prevented from sliding and displacement from a desired position on wires. This invention further relates to a method for mounting a noise filter on a wire. This invention additionally relates to a combination of a noise filter and a wire.
2. Description of Related Art
FIG. 7 shows a conventional noise filter 1 provided on wires to absorb electromagnetic noise. The noise filter 1 has a case 2, which can be separated into halves, and a cylindrical ferrite core 3 provided inside of the case 2. When this type of noise filter 1 is used, to improve the noise absorbing effect, wires W pass through a wire insertion through-hole 3a provided in the ferrite core 3 and are looped at least once to wind around the outside of the case 2 in an axial (longitudinal) direction of the cylindrical ferrite core 3. In this case, since the wires W are wound around the outside of the case 2, the noise filter 1 is prevented, to some extent, from sliding on the wires W or displacing from a predetermined position. However, conventionally, a tie band 4 is provided to securely fix the noise filter 1 at the predetermined position on an outer periphery of the wires W.
To fix the noise filter 1 to the wires W by using the tie band 4, as described above, a fixing operation is required in which the tie band is inserted into the loop of wires W and the wires that are looped to wind around the outside of the case 2 and pass back through the ferrite core 3 and the wires directly passing into the ferrite core 3 should be fastened together with the tie band 4. However, such a fixing operation using the tie band 4 is troublesome, tends to vary depending on operators, and causes unstable quality of products.
The present invention is provided in view of the above-described problems. An objective of the present invention is to provide a noise filter that can be securely fixed at a predetermined position on the wires and to improve the effectiveness of a mounting operation of the noise filter on the wires.
To achieve the above and/or other goals, the present invention provides a noise filter that includes a core having a wire insertion through-hole extending in a longitudinal direction of the core, a case that covers the core, and a wire fixing portion provided on an outer surface of the case so as to hold the wires passing through the wire insertion through-hole and looped to wind around the outside of the case. The core absorbs electromagnetic noise.
According to the construction described above, when the noise filter is mounted around the wires and the wires are looped to wind around the outside of a case of the noise filter, the wire fixing portion holds and fixes the wires in position. Accordingly, the noise filter is prevented from being displaced from a predetermined position or from sliding on the wires, and thus, is securely fixed on the wires.
The wire fixing portion can include a pressing surface provided on the outer surface of the case, and a pressing portion that faces the pressing surface and can be opened from and closed toward the pressing surface, the wire being held between the pressing surface and the pressing portion.
A stopper including at least one ridge and at least one trough can be formed on at least one of the pressing surface and a surface of the pressing portion facing the pressing surface. It is also possible to provide a stopper including at least one depression formed in one of the pressing surface and a surface of the pressing portion facing the pressing surface, and at least one projection formed in another one of the pressing surface and the surface of the pressing portion facing the pressing surface.
According to the construction described above, the wires looped to wind around the outside of the case can be sandwiched between the pressing portion and the pressing surface. Further, the wires are more positively fixed to the noise filter by the stopper provided on facing surfaces of the pressing portion and the pressing surface.
Further, the wire fixing portion can include interengaging locking elements respectively provided on the pressing portion and on the case. The interengaging locking elements cooperate to lock the pressing portion to the outer surface of the case to hold the wire in position. The interengaging locking elements may include a locking hook and a locking hole. The interengaging locking elements lock the pressing portion to the outer surface of the case by inserting the locking hook into the locking hole.
The wire fixing portion can further include a hinge connecting an edge of the pressing surface and an edge of the pressing portion along a longitudinal direction of the core. In this case, the interengaging locking elements may be provided at an edge opposite the edge where the hinge is placed.
The wire fixing portion can be formed separately from the case. In this case, a plurality of interengaging locking elements are respectively provided on the wire fixing portion and on the case to retain the wire fixing portion in position to hold the wire.
According to the construction as described above, while the wires are placed between the pressing portion and the pressing surface, the pressing portion is pressed toward the outer surface of the case. Thus, the pressing portion can be locked with the outer surface of the case with a single operation.
Preferably, the case is formed to have a cylindrical shape. The wire fixing portion can be placed on an outer peripheral surface of the case or on an end face of the case.
Preferably, the noise filter is formed into at least two separable portions and at least one of the separable portions has at least a portion of the wire insertion through-hole. Further, it is preferable that the wire fixing portion is provided on one of the separable portions in which the at least portion of the wire insertion through-hole is provided.
In another aspect of the present invention, there is provided a method of mounting a noise filter on a wire, including inserting the wire into a wire insertion through-hole extending in a longitudinal direction of the noise filter and looping the wire so that the wire winds around the noise filter, placing the wire on an exterior of the noise filter on a pressing surface of a wire fixing portion provided on an outer surface of the noise filter, and closing a pressing portion of the wire fixing portion toward the pressing surface so that the wire is held between the pressing surface and the pressing portion.
Preferably, the inserting of the wire into the wire insertion through-hole and looping of the wire include providing the noise filter separable into at least two portions, and separating the noise filter into the at least the two portions. At least one of the separated portions has at least a portion of the wire insertion through-hole. The inserting further includes winding of the wire at least once around one of the separated portions of the noise filter so that the wire is aligned in the direction of the wire insertion through-hole, and closing the at least two portions together to form a single unit.
Thus, the operation for mounting a noise filter on a wire can be achieved by simply and easily.